A

orbbyn©

K

1

t3aRtipetmII

0

Industrial Crops and Products 26 (2007) 259–264

Pulping and papermaking properties of pati (Typha)

M. Sarwar Jahan a,∗, M. Khalidul Islam a, D.A. Nasima Chowdhury a,S.M. Iqbal Moeiz b, U. Arman b

a Pulp and Paper Research Division, BCSIR Laboratories, Dhaka, Bangladeshb Department of Chemistry, Dhaka College, Dhaka 1205, Bangladesh

Received 18 May 2005; accepted 26 March 2007

bstract

Pati grown in the northern and eastern region of Bangladesh was submitted to chemical and morphological analysis. The resultsf general chemical analysis have evidenced the different relative abundance of holocellulose, lignin, extractive and ash. The easternegion pati had higher holocellulose and lower lignin and extractives than the northern region pati. Morphological properties of

oth regions pati were similar. Pulping of northern and eastern region pati was done with varying active alkali and cooking time atoiling temperature. The viscosity of pati pulp was increased with decreasing kappa number. Eastern region pati had higher pulpield and lower kappa number than northern region pati. Initial SR value and strength properties of pati were higher than otheronwood. Eastern region pati showed higher strength properties than northern region pati.

2007 Elsevier B.V. All rights reserved.

ngth pr

eywords: Grass; Low temperature pulping; Freeness; Viscosity; Stre

. Introduction

Paper consumption is continuously increasing acrosshe world. World paper consumption was about00 million tonnes in 1996–1997 and is expected to risebove 400 million tonnes by the year 2010 (Hurter andiccio, 1998). The available wood supply in many coun-

ries will not meet the growing demand. Much of thisncrease in fiber demand will be met by increased forestryroduction in tropical countries, but higher fiber recov-ry rates and the use of nonwood fibers will also playheir part. Today, the use of nonwood fibers is com-

on in wood-limited countries. For example, China andndia are the two largest producers of nonwood pulp.n China, the nonwood pulping capacity is 80% of the

∗ Corresponding author. Tel.: +880 2 8920480; fax: +880 2 8613022.E-mail address: m sarwar@bdonline.com (M.S. Jahan).

926-6690/$ – see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.indcrop.2007.03.014

operties

country’s total pulping capacity, while in India it is 60%.Thus, research interest is growing in tropical countrieslike Bangladesh on potential substitute (nonwood) ofwood for pulping purpose. Agricultural residues, dif-ferent kinds of grass, annual plants are the importantnonwood fibers for pulping.

The inherent problem of grass and straw in pulping isthe high content of small parenchyma cells, giving multi-plicity of so-called primary fines in the pulp. These cellsfurther disintegrate during the beating operation givingan additional quantity of so-called secondary fines. Thisbehavior limits the utilization of grasses as pulping rawmaterials. Zhao et al. (1992) suggested that the pulps,which contain a large fraction of primary fines should beused in the unbeaten state. Another draw back of grass

and straw is collection, which limits to build up full-sizepulp mill based on grass and straw.

Recently, Bangladesh government has bannedpolyethylene bag to protect the environment. Therefore,

rops an

3.1. Chemical and morphological characteristics

Table 1 shows that a comparative chemical and mor-phological analysis results of pati obtained from the

Table 1Chemical and morphological properties of pati

Northern region Eastern region

Extractive (%)Hot water 12.7 11.91% alkali 39.1 38.2Dichloromethane 1.4 1.3

Klason lignin (%) 16.8 16.2Pentosan (%) 33.6 31.2

260 M.S. Jahan et al. / Industrial C

40,000 workers in about 400 polyethylene bag factorieshave lost their jobs. So, interest is growing up to buildbiodegradable bag industry. Many cottage industries aregrowing for manufacturing paper bag based on recyclingpaper. These bags could not meet the demand of user,because of lower strength. Different types of grass aregrown in the different region of Bangladesh. The quantityof these grasses is too low in respect to set up a pulp mill.Also drainage resistance of these grasses is very high.Therefore, a few cottage pulp mills could be set up for themanufacture of handmade paper. Pati (Typha) is one kindof grass. It grows in the different regions of Bangladesh.The properties of pati will vary with the geographicallocation. The objectives of the present investigation areto (1) characterize chemical and morphological proper-ties of pati grown in different regions, (2) pulping of thetwo different region pati with varying active alkali andcooking time at boiling temperature, and (3) also pulpingat higher temperature with varying active alkali and time.

2. Materials and methods

2.1. Materials

Pati was collected from northern and eastern regionof Bangladesh and sun dried. The pati was cut to 2–3 cmin length. The moisture content of pati was determinedfor the subsequent experiments.

2.2. Morphological properties

For the measurement of fiber length, pati was macer-ated in a solution containing 1:1 HNO3 and KClO3. Adrop of macerated sample was taken on a slide and fiberlength was measured under a profile projector (NikonV-12, Japan).

2.3. Chemical analysis

The hot water solubility (T207 cm99), 1% alkali sol-ubility, extractives (T204 om88), Klason lignin (T222om98), viscosity (T230 om99) and ash content (T211om93) were determined in accordance with Tappi TestMethods. Holocellulose was determined by treatingextractive-free wood meal with NaClO2 solution. ThepH of the solution was maintained at 4 by adding acetatebuffer.

2.4. Pulping

Pulping of pati was done in an electrically heated opendigester with constant stirring device. The pulping wascarried out under the following conditions:

d Products 26 (2007) 259–264

• Active alkali: 8, 10 and 12% as NaOH.• Time: 60, 90 and 120 min at the boiling temperature.• Liquor to feedstock ratio: 8:1.• Temperature: boiling.

During cooking, the constant volume of the liquorinside the digester was maintained by adding hot water.

For the high temperature pulping, eastern region patiwas cooked in a 5 l capacity batch cylindrical digesterheated by means of electrical resistance and a motorrotated it. The normal charge was 300 g of moisture freepati. The temperature (120, 130 and 140 ◦C) and alkali(8, 10 and 12%) were varied. The time to raise maxi-mum temperature was 50 min. The liquor ratio was heldconstant at 6.

After completing digestion time, pulp was washedwith tap water till the removal of all chemicals. Theyield of the pulp was determined gravimetrically fromthe oven-dried weight of pati.

2.5. Evaluation of pulps

Pati pulps were disintegrated in a standard disinte-grator. The handsheets of about 60 g/m2 were made in aRapid Kothen Sheet Making Machine according to Ger-man Standard Methods number 106. The sheets weretested for tensile (T494 om-96), burst (T403 om-97), andtear strength (T414 om-98) according to TAPPI StandardTest Methods.

3. Results and discussion

Holocellulose (%) 71.0 70.6Cellulose (%) 34.4 36.8Ash (%) 3.7 3.5Fiber length (mm) 1.3 1.3Fiber diameter (�m) 12.0 13.2

rops and Products 26 (2007) 259–264 261

nseiefaaTmecaTwmtttvpfhiwlostc1

3

ian

TE

A

11

11

11

M.S. Jahan et al. / Industrial C

orthern and eastern region of Bangladesh. There wasome difference of chemical and morphological prop-rties of the two regions. The northern pati was richern extractives than eastern. The hot water and 1% alkalixtracts of the northern pati were 12.7 and 39.1%, whileor the eastern pati the amount of extracts were 11.9nd 38.2%, respectively. These extractives were highers compared to other grasses (Radiotis et al., 1999).he high hot water solubility revealed the presence ofany soluble carbohydrates and phenolics as well as the

ffect of parenchyma and porosity of the tissue. Typi-al high solubility in 1% NaOH indicated easy accessnd degradation of the cell wall material by weak alkali.he Klason lignin in pati was very low as compared toood (Goyal et al., 1999). An easier pulping in alkalineedium is also expected from their lower lignin con-

ent. The Klason lignin in northern pati was a little higherhan in eastern (16.8 versus 16.2). The holocellulose con-ent in the northern pati was higher than in eastern (71.0ersus 70.6). The �-cellulose and pentosan in northernati were 34.4 and 33.6%, while those of determinedor eastern pati were 36.8 and 31.2%, respectively. Theigh pentosan in pati anticipated high bonding strengthn the unbeaten pulp. The ash content in northern patias higher than in eastern pati (3.7 versus 3.5). Fiber

ength is an important parameter in papermaker pointf view. Fiber dimensions of both regions pati showedimilar results with length of 1.3 mm and with diame-er of 13.2 �m. These fiber dimensions were very closeompared thistle (Cynara cardunculus L.) 1.3 mm and8.8 �m, respectively (Gominho et al., 2001).

.2. Low temperature pulping

Soda pulping of pati feedstocks was done using vary-ng cooking time and active alkali at boiling temperaturend data are shown in Table 2. Pulp yield and kappaumber were decreased with increasing cooking time

able 2ffect of different parameter on pulp yield, kappa number and viscosity of pu

lkali (%) Cooking time (min) Pulp yield

Northern Eastern

8 60 53.5 54.70 60 51.5 52.32 60 50.0 51.18 90 52.2 52.60 90 50.2 51.02 90 48.1 48.78 120 49.4 50.20 120 48.1 48.32 120 46.7 46.9

Fig. 1. Relationship between yield and kappa number of pulp obtainedfrom pati.

or active alkali. Eastern pulp showed higher pulp yieldand lower kappa number than northern pati. In 60 min ofcooking, pulp yield of northern pati was decreased from53.5 to 50.0% with increasing active alkali from 8 to12%, while eastern pati from 54.7 to 51.1%. At the samecondition, kappa number was decreased 25.1–23.6 fornorthern pati and 24.8–23.1 for eastern pati. Similarlypulp yield and kappa number decreased with increasingactive alkali at any constant cooking time. In 120 minof cooking at 10% active alkali, 0.8% higher pulp yieldwith almost similar kappa number was observed in east-ern pati. Fig. 1 shows the relationship between pulp yieldand kappa number of northern and eastern region of pati.Eastern pati had higher pulp yield at any kappa num-ber than northern pati. As shown in Table 1 viscosity ofpati increased with increasing active alkali and cookingtime. The highest viscosity 26.8 mPa s was obtained foreastern pati in 120 min of cooking at 12% active alkali.

Fig. 2 shows the relationship between kappa numberand viscosity. Viscosity was decreased with decreasingkappa number. Generally in wood pulping, viscositydecreases as kappa number fall increases, indicating

lp obtained from pati

Kappa number Viscosity (mPa s)

Northern Eastern Northern Eastern

25.1 24.8 18.8 19.824.5 24.1 20.8 21.323.6 23.1 21.7 22.723.8 22.2 20.9 21.518.3 18.4 22.6 23.116.4 16.3 23.5 24.421.4 21.1 22.4 22.717.2 16.8 25.1 25.715.2 15.1 25.9 26.8

262 M.S. Jahan et al. / Industrial Crops and Products 26 (2007) 259–264

Fig. 2. Relationship between viscosity and kappa number of pati pulps.

cellulose depolymerization (Sjoblom, 1996). However,this trend was not found in our present investigation.This can be explained with high content of pentosanin pati (Table 1). The hemicellulose and lignin in patiwere simultaneously removed during cooking of pati.Therefore, high yield together with high kappa num-ber resulted in lower viscosity of pulp. Thus understrong cooking conditions, significant dissolution ofhemicellulose caused a significant increase of viscos-ity. Similar results were observed in soda-AQ pulpingof reed canary grass (Feng and Alen, 2001). The lowestviscosity 19.8 mPa s was obtained at kappa number 24.8and highest 26.8 mPa s at kappa number 15.1 for east-ern pati pulp, while viscosity was obtained 18.8 mPa sat kappa number 25.1 and 25.9 mPa s at kappa number15.2 for northern pati pulp.

3.3. Physical properties

The strength properties of unbleached pati pulp weredetermined in the unbeaten state. Our main objective ofthis study was to utilize pati as a source of raw materials

Table 3Effect of different parameter on physical properties of pulps obtained from pa

Alkali (m) Cooking time (min) Breaking length (m)

Northern Eastern

8 60 5414 557410 60 5639 582312 60 5789 5966

8 90 5587 567510 90 5747 589212 90 5798 6024

8 120 5584 572410 120 5842 604512 120 5976 6121

Fig. 3. Comparison of pulp strength properties of pati pulp at lowtemperature cooking.

for handmade paper. Therefore, beating of pati pulp wasavoided. In the unbeaten state SR value of pati pulp werevery high (about 45). The strength properties of pati pulpwere increased with increasing cooking time or activealkali. These results were consistent with viscosity data.The eastern pati pulp showed higher strength propertiesthan northern pati pulp. Pulps cooked with 10% activealkali for 90 min, had a breaking length of 5890 mfor eastern and 5750 m for northern pati pulp, and aburst index of 3.6 and 3.4 kPa m2/g and a tear indexand 13.4 and 12.6 mN m2/g, respectively (Table 3).These results are quite high for the unbeaten pulps. C.cardunculus L. whole stalks (Gominho et al., 2001) had6300 m breaking length, 3.4 kPa m2/g burst index and6.7 mN m2/g tear index. Fig. 3 shows the comparison

of strength properties of low temperature pati pulpobtained from the two different regions. Easter patishowed higher tensile, tear and burst index than northernpati.

ti

Burst index (kPa m2/g) Tear index (mN m2/g)

Northern Eastern Northern Eastern

3.1 3.3 12.1 13.23.3 3.3 12.4 13.43.4 3.5 12.4 13.73.2 3.3 12.0 13.33.4 3.6 12.6 13.43.6 3.7 12.8 13.63.2 3.4 11.9 12.43.5 3.5 12.3 12.53.7 3.7 12.0 12.3

M.S. Jahan et al. / Industrial Crops and Products 26 (2007) 259–264 263

Table 4Effect of temperature and alkali on the pulp yield and pulp properties of pati

Temp Activealkali (%)

Pulpyield (%)

Kappanumber

0SR Breakinglength (m)

Bursting strength(kPa m2/g)

Tear index(mN m2/g)

120 8 48.9 18.8 44 7158 4.3 15.3130 8 45.7 17.6 47 7485 4.8 14.7140 8 42.4 16.3 47 7744 5.0 14.1120 10 45.1 16.4 49 8074 5.3 14.6130 10 42.9 14.5 50 8526 5.8 14.9140 10 40.8 13.2 50 8561 5.8 14.1120 12 41.8 14.2 51 8123 5.8 13.21 50 8008 5.7 13.41 50 8102 5.3 12.7

3

ambaatait4ctkadttwteli1irnaaauctstp

Eastern region pati pulp obtained from both low andhigh temperature cooking was beaten in PFI mill todifferent SR values in order to measure strength prop-

30 12 39.2 13.440 12 37.8 11.9

.4. High temperature pulping

One set of experiments was done at higher temper-ture in order to know the properties of pati pulp asachine made paper. Easter region pati, which showed

etter properties in boiling cooing was cooked in 8, 10nd 12% active alkali for 60 min at 120, 130 and 140 ◦Cnd its results are shown in Table 4. At higher tempera-ure, pulp yield was lost significantly, but kappa numberlso reduced. Pulp yield was lost severely with thencrease of alkali from 8 to 10% at higher temperature. Athe temperature of 140 ◦C, pulp yield was decreased from2.4 to 37.8% with a kappa number drop of 4.4 units. Pro-essing of pati at higher reaction temperature increasedhe delignification ability of the pulping system. It is wellnown that a certain number of �-O-4 and �-O-4 link-ges within the lignin macromolecule must be cleaved toissolve lignin during pulping so that it can be degradedo lower molecular weight fragments that are soluble inhe system. The drainage resistance (0SR) was very high,hich limits the use pati as of machine made paper. In

he unbeaten state, strength properties were very high,specially breaking length and burst index. The breakingength was increased from 8074 to 8561 m with increas-ng temperature from 120 to 140 ◦C with alkali level of0%. Strength properties were deteriorated with furtherncrease in alkali concentration within this temperatureange. Pati contains primary fines, which are predomi-antly thin-walled parenchyma cells. These parenchymare easily deformed and increase SR value (Chang etl., 1994). Even though pati fines increased SR valuend water retention, they improve the tensile strength ofnbeaten pulp. The thin-walled parenchyma cells mustollapse that aided in fiber bonding and contributing to

he tensile strength (Watson and Garner, 1997). The teartrength was decreased a bit with increasing tempera-ure, but remained still higher than in low temperatureati pulp.

Fig. 4. Effect of PFI revolution of freeness (0SR).

3.5. Beating effect

Fig. 5. Freeness (0SR) vs. breaking length.

264 M.S. Jahan et al. / Industrial Crops an

Fig. 6. Freeness (0SR) vs. burst index.

erties of beaten pulp. Initial SR value of pati pulpwas very high; therefore, only 500 PFI revolutionsincreased SR value to 62 and 56 for high and lowtemperature cooking, respectively (Fig. 4). This mayalso be attributed by high fines content. The break-ing length first increased then decreased (Fig. 5). Theburst index increased slightly with increasing SR num-

ber (Fig. 6). The tear index decreased with increasingbeating degree (Fig. 7). All strength properties of ‘hightemperature pulp’ were better than in ‘low temperaturepulp’.

Fig. 7. Freeness (0SR) vs. tear index.

d Products 26 (2007) 259–264

4. Conclusions

Pati is characterized with high extractive and pen-tosan, and low lignin and cellulose. Eastern pati hasbetter chemical properties and similar morphologicalproperties compared to northern pati. Pulp yield andkappa number decreased with increasing active alkalior cooking time at the boiling temperature. Increasedpulp viscosity was observed with decreasing kappa num-ber. High SR value and strength properties of pati pulpwere observed in the unbeaten state. Eastern pati showedimproved pulp yield and physical properties in contrastto northern pati. Pulp yield was severely lost at hightemperature pulping of pati, but produced pulp of highstrength properties. From the above results, it may con-clude that pati would be a good source for handmadepaper in the cottage industry.

References

Chang, Z., Leminen, J., Ala-Kaila, K., Paulapuro, H., 1994. The basicdrainage properties of Chinese wheat straw pulp. In: Pulping Con-ference Proceedings. Tappi Press, Atlanta, p. 735.

Feng, Z., Alen, R., 2001. Soda-AQ pulping of reed canary grass. Ind.Crops Prod. 14 (1), 31–39.

Gominho, J., Fernandez, J., Pereira, H., 2001. Cynara cardunculusL.—a new fiber crop for pulp and paper production. Ind. CropsProd. 13 (1), 1–10.

Goyal, G.C., Fisher, J.J., Krohn, M.J., Packwood, R.E., Olson, J.R.,1999. Variability in pulping and fiber characteristics of hybridpoplar tree due to their genetic makeup, environmental factors andtree age. Tappi J. 53 (5), 141–147.

Hurter, R.W., Riccio, F.A., 1998. Why CEOS don’t want to hear aboutnonwoods—or should they? In: TAPPI Proceedings, NA NonwoodFiber Symposium, Atlanta, GA, USA, pp. 1–11.

Radiotis, T., Li, J., Goel, K., Eisner, R., 1999. Fiber characteristics, pul-pability, and bleachability of switchgrass. Tappi J. 82 (7), 100–105.

Sjoblom, K., 1996. Extended delignification in kraft cooking throughimproved selectivity. Part 5. Influence of dissolved lignin on therate of delignification. Nord. Pulp Pap. Res. J. 11 (3), 177–185,191.

Watson, P., Garner, A., 1997. The opportunities for producing pulpfrom agriculture residues in Alberta. In: A Review of Non-

wood Pulping Technologies, Pulp and Paper Research Institute ofCanada, Miscellaneous report, MR 355.

Zhao, X., Odberg, L., Risinger, G., 1992. Beating of wheat-straw pulp:dissolved carbohydrates and lignins, fiber swelling and fines gen-eration. Tappi J. 75 (1), 153.